Could 'tiny grazers' help save the Caribbean coral reefs?

Miniature species of urchin and parrotfish eat up suffocating algae.

9th January 2017
Could 'tiny grazers' save the Caribbean coral reefs? © Smithsonian Tropical Research Institute

Two miniature species of algae-grazer could offer new hope in the Caribbean, where an overgrowth of algae threatens to wipe out coral reefs.

In 1984, a mysterious disease obliterated the local population of algae-eating black sea urchins, leading to an overgrowth of algae that smothered the coral reefs. Overfishing in the region has also reduced the numbers of algae-grazing parrotfish, further exacerbating the problem.

But a new study carried out by the Smithsonian Tropical Research Institute suggests that pocket-sized versions of these grazers could keep the algae in check. Exploring a large area of the sea floor in Bocas del Toro, Panama, the researchers used underwater cages with gaps too small to allow the larger parrotfish and urchin species in to feed on the algae.

They discovered that the smaller species could clear the coral of algae just as effectively. One of these, the urchin Echinometra viridis, is about the size of a tangerine, while the researchers also found the finger-sized striped parrotfish Scarus iseri on the algae-dominated reefs. Other small species like these made up 95 per cent of the grazers observed on the coral.

"These dollhouse-sized species came to the rescue of reefs in Panama, and may be important elsewhere," says study co-author Andrew Altieri.

The researchers now hope to demonstrate that this algae clearance is allowing new coral to grow. With a 2014 report warning that most coral reefs could disappear from the Caribbean within 20 years, conservationists will hope that it's not too little, too late.